In a next generation communication system, a QoS level for each kind of service class is measured and congestion detection is given priority in performance according to the measured level, thereby taking suitable measurements.
The next generation communication system employs an algorithm in which a delay between the service classes is measured and when the number of the measured values continuously exceeding a predetermined value is greater than a specific number, the system is detected that it is in a congestion state. However, in the above algorithm, there are problems in that reactions with priority for the congestion state are insufficient. Further, the congestion state is detected only when the number of the measured delays between the service classes continuously exceeding the predetermined value is greater than the specific number. Therefore, the congestion state may not be detected accurately depending on traffic patterns.